The fourth Gordon Research Conference on the Biology of Spirochetes will be held in January, 2000 in Ventura, California. This conference is the only ongoing international meeting devoted to basic research of all medically important and biologically relevant spirochetes, a unique group of Eubacteria. Pathogenic spirochetes include those that cause syphilis, Lyme disease, relapsing fever, leptospirosis, periodontal disease, digital dermatitis of cattle, and swine and human dysentery. As a group, these organisms have historically been difficult to study because of the lack of a system for continuous in vitro culture (in some cases) and the relatively primitive status of genetic systems for mutational analysis. However, the recent publication of the genomic sequences for Borrelia burgdorferi and Treponema pallidum, and a newly initiated project for sequencing the Treponema denticola genome, provide a wealth of new information that is now being incorporated into ongoing studies on the physiology, structure, pathogenesis, and immunobiology of these bacteria. The first three Biology of Spirochetes conferences were well-received, achieving maximal attendance and high ratings. For the 2000 conference, it is anticipated that the maximal number of 150 faculty, graduate students, postdoctoral fellows, and industrial scientists will attend. As in previous conferences, a broad spectrum of scientists of different research interests, geographic locations, and seniority will be included. Special attention will be payed to the adequate representation of young investigators at the graduate student, postdoc, and junior faculty levels, as well as an appropriate balance in terms of gender and ethnicity. The planned oral presentations and poster sessions will provide a forum for discussion, exchange of ideas, and development of collaborations. Funding from the National Institutes of Health is requested to partially offset the travel and registration expenses of the speakers, discussion leaders, and participating graduate students, fellows, and junior faculty members.